Steps to reproduce:

1. Create a new Unity project using the Universal 3D template
2. Install the Animation Rigging package (com.unity.animation.rigging)
3. Select the "Global Volume" GameObject in the Hierarchy window
4. Open the Animation Rigging dropdown in the toolbar
5. Select "Rig Setup"
6. Click the "Add/""" button in the Animation Rigging Scene Overlay
7. Observe the Animation Rigging Scene Overlay
8. Deselect the "Global Volume" GameObject in the Hierarchy window
9. Repeat step 3
10. Repeat step 7
11. Click the "Remove/"-"" button in the Animation Rigging Scene Overlay
12. Repeat step 7
13. Repeat step 11
14. Observe the Console window

Actual results: The Animation Rigging Scene Overlay does not update until the GameObject is deselected and selected again, which leads to "NullReferenceException" errors being thrown when removing elements from the Animation Rigging Scene Overlay

Expected results: The Animation Rigging Scene Overlay updates when "Add/""" or "Remove/"-"" buttons are pressed

Reproducible with versions: 1.3.1, 1.4.0 (6000.0.62f1, 6000.2.12f1, 6000.3.0f1, 6000.4.0a5, 6000.5.0a1)

Tested on (OS): MacOS Silicon Tahoe 26.0.1, Windows 11